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<p>创建Test.java 文件</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">import</span>  java.lang.*;<span class="comment">//编译器默认已导入jar包，System类可使用</span></span><br><span class="line"><span class="keyword">public</span>  <span class="keyword">class</span> <span class="title class_">Test</span>&#123;</span><br><span class="line">		<span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span>&#123;</span><br><span class="line">			System.out.print(<span class="string">&quot;gghgh&quot;</span>);</span><br><span class="line"></span><br><span class="line">			   <span class="comment">// 字符型</span></span><br><span class="line">				<span class="type">char</span> <span class="variable">webName1</span> <span class="operator">=</span> <span class="string">&#x27;微&#x27;</span>;</span><br><span class="line">				<span class="type">char</span> <span class="variable">webName2</span> <span class="operator">=</span> <span class="string">&#x27;学&#x27;</span>;</span><br><span class="line">				<span class="type">char</span> <span class="variable">webName3</span> <span class="operator">=</span> <span class="string">&#x27;苑&#x27;</span>;</span><br><span class="line">				System.out.println(<span class="string">&quot;网站的名字是：&quot;</span> + webName1 + webName2 + webName3);</span><br><span class="line">			       </span><br><span class="line">				<span class="comment">// 整型</span></span><br><span class="line">				<span class="type">short</span> x=<span class="number">22</span>;  <span class="comment">// 十进制</span></span><br><span class="line">				<span class="type">int</span> y=<span class="number">022</span>;  <span class="comment">// 八进制</span></span><br><span class="line">				<span class="type">long</span> z=<span class="number">0x22L</span>;  <span class="comment">// 十六进制</span></span><br><span class="line">				System.out.println(<span class="string">&quot;转化成十进制：x = &quot;</span> + x + <span class="string">&quot;, y = &quot;</span> + y + <span class="string">&quot;, z = &quot;</span> + z);</span><br><span class="line">			       </span><br><span class="line">				<span class="comment">// 浮点型</span></span><br><span class="line">				<span class="type">float</span> <span class="variable">m</span> <span class="operator">=</span> <span class="number">22.45f</span>;</span><br><span class="line">				<span class="type">double</span> <span class="variable">n</span> <span class="operator">=</span> <span class="number">10</span>;</span><br><span class="line">				System.out.println(<span class="string">&quot;计算乘积：&quot;</span> + m + <span class="string">&quot; * &quot;</span> + n + <span class="string">&quot;=&quot;</span> + m*n);</span><br><span class="line">				</span><br><span class="line">				<span class="type">boolean</span> <span class="variable">aa</span> <span class="operator">=</span><span class="number">100</span> &gt; <span class="number">10</span>;</span><br><span class="line">				<span class="type">boolean</span> <span class="variable">bb</span> <span class="operator">=</span><span class="number">100</span> &lt; <span class="number">10</span>;</span><br><span class="line">				System.out.println(<span class="string">&quot;100&gt;10 = &quot;</span> + aa);</span><br><span class="line">				System.out.println(<span class="string">&quot;100&lt;10 = &quot;</span> + bb);</span><br><span class="line">				   </span><br><span class="line">				<span class="keyword">if</span>(aa)&#123;</span><br><span class="line">					System.out.println(<span class="string">&quot;100&lt;10是对的&quot;</span>);</span><br><span class="line">				&#125;<span class="keyword">else</span>&#123;</span><br><span class="line">					System.out.println(<span class="string">&quot;100&lt;10是错的&quot;</span>);</span><br><span class="line">				&#125;		</span><br><span class="line">				</span><br><span class="line">				</span><br><span class="line">				<span class="comment">//定义一个名为student类</span></span><br><span class="line">				<span class="keyword">class</span> <span class="title class_">Student</span>&#123;  <span class="comment">// 通过class关键字类定义类</span></span><br><span class="line">					<span class="comment">// 类包含的变量</span></span><br><span class="line">					String name;</span><br><span class="line">					<span class="type">int</span> age;</span><br><span class="line">					<span class="type">float</span> score;</span><br><span class="line">					<span class="comment">// 类包含的函数</span></span><br><span class="line">					<span class="keyword">void</span> <span class="title function_">say</span><span class="params">()</span>&#123;</span><br><span class="line">						System.out.println( name + <span class="string">&quot;的年龄是 &quot;</span> + age + <span class="string">&quot;，成绩是 &quot;</span> + score);</span><br><span class="line">					&#125;</span><br><span class="line">					</span><br><span class="line">					<span class="keyword">void</span> <span class="title function_">sayhelloworld</span><span class="params">()</span>&#123;</span><br><span class="line">						System.out.print(name + <span class="string">&quot;年龄 &quot;</span> +age +<span class="string">&quot;成绩 &quot;</span> +score);</span><br><span class="line">						</span><br><span class="line">					&#125;</span><br><span class="line">				&#125;</span><br><span class="line">				<span class="comment">// 通过类来定义变量，即创建对象</span></span><br><span class="line">				<span class="type">Student</span> <span class="variable">stu1</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Student</span>();  <span class="comment">// 必须使用new关键字</span></span><br><span class="line">				<span class="comment">// 操作类的成员</span></span><br><span class="line">				stu1.name = <span class="string">&quot;小明&quot;</span>;</span><br><span class="line">				stu1.age = <span class="number">15</span>;</span><br><span class="line">				stu1.score = <span class="number">92.5f</span>;</span><br><span class="line">				stu1.say();</span><br><span class="line">				</span><br><span class="line">				<span class="type">Student</span> <span class="variable">stu2</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Student</span>();  <span class="comment">// 必须使用new关键字</span></span><br><span class="line">				<span class="comment">// 操作类的成员</span></span><br><span class="line">				stu2.name = <span class="string">&quot;小吉&quot;</span>;</span><br><span class="line">				stu2.age = <span class="number">16</span>;</span><br><span class="line">				stu2.score = <span class="number">94.7f</span>;</span><br><span class="line">				stu2.sayhelloworld();</span><br><span class="line">		&#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>


<p><strong>Java中print、printf、println的区别</strong></p>
<p>printf主要是继承了C语言的printf的一些特性，可以进行格式化输出<br>print就是一般的标准输出，但是不换行<br>println和print基本没什么差别，就是最后会换行<br>System.out.printf(“the number is: d”,t);</p>
<p><strong>参照JAVA API的定义如下：</strong>‘d’ 整数 结果被格式化为十进制整数<br>‘o’ 整数 结果被格式化为八进制整数<br>‘x’, ‘X’ 整数 结果被格式化为十六进制整数<br>‘e’, ‘E’ 浮点 结果被格式化为用计算机科学记数法表示的十进制数<br>‘f’ 浮点 结果被格式化为十进制数<br>‘g’, ‘G’ 浮点 根据精度和舍入运算后的值，使用计算机科学记数形式或十进制格式对结果进行格式化。<br>‘a’, ‘A’ 浮点 结果被格式化为带有效位数和指数的十六进制浮点数<br>println(“test”)相当于print(“testn”)就是一般的输出字符串</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">int</span> <span class="variable">i</span> <span class="operator">=</span> <span class="number">4</span>;</span><br><span class="line"><span class="type">double</span> <span class="variable">j</span> <span class="operator">=</span> <span class="number">5</span>;</span><br><span class="line">System.out.print(<span class="string">&quot;用print输出i:&quot;</span>+ i);</span><br><span class="line">System.out.println( <span class="string">&quot;用println输出i:&quot;</span>+ i);</span><br><span class="line">System.out.printf(<span class="string">&quot;i的值为%d,j的值为%f&quot;</span>, i,j);</span><br></pre></td></tr></table></figure>




<p>断点调试命令</p>
<p>直接在控制台输入help，即可看到相关调试命令</p>
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